1. Field of the Invention
The present invention relates to a radiation-sensitive resin composition useful as a chemically amplified resist for microfabrication using various radiations, in particular, deep ultraviolet rays such as a KrF excimer laser and ArF excimer laser, charged particle rays such as electron beams, and X-rays.
2. Description of the Background Art
In the field of microfabrication exemplified by the manufacture of an integrated circuit device, development of a lithographic process capable of reproducing microfabrication with a line-width precision of 0.5 μm or less has been pursued in recent years to achieve higher integration. To ensure microfabrication in the order of 0.5 μm or less, a resist which can excellently reproduce patterns with a 0.5 μm or less line-width has been required. However, it is difficult to produce such a minute pattern at high precision by conventional methods using visible light (wavelength: 800-400 nm) or near ultraviolet light (wavelength: 400-300 nm). For this reason, the use of radiation with a shorter wavelength (wavelength: less than 300 nm) has been studied.
As examples of such short wavelength radiation, a bright line spectrum of a mercury lamp (wavelength: 254 nm), deep ultraviolet rays typified by a KrF excimer laser (wavelength: 248 nm) and an ArF excimer laser (wavelength: 193 nm), charged particles such as electron beams, and X-rays such as synchrotron radiation can be given. Of these, lithography using an excimer laser is regarded as promising due to high output and high efficiency. Lithography using an excimer laser requires a resist which can reproduce fine patterns with a dimension of 0.5 μm or less at high sensitivity and high resolution.
Chemically amplified resists comprising a photoacid generator which forms an acid upon irradiation with radioactive rays (hereinafter called “exposure”) have been proposed as resists applicable to deep ultraviolet ray such as an excimer laser. The sensitivity of the chemically amplified resist is increased by the catalytic action of the acid thus formed.
As such a chemically amplified resist, Japanese Patent Application Laid-open No. 45439/1984 discloses a combination of a resin protected with a t-butyl group or a t-butoxycarbonyl group and a photoacid generator. Japanese Patent Application Laid-open No. 52845/1985 discloses a combination of a resin protected by a silyl group and a photoacid generator. In addition to these resist compositions, there are a number of reports dealing with chemically amplified resists, such as a resist which contains a resin protected by an acetal group or a ketal group and a photoacid generator (Japanese Patent Application Laid-open No. 25850/1990).
Of these chemically amplified resists, those in which a resin having an acetal group or ketal group is used are attracting attention due to their high resolution capability (e.g. Proc. SPIE Vol. 3049, Page 314).
However, when a stringent line-width control is required such as in the case of fabricating devices with sub-half micron or less dimensions, resolution capability alone is insufficient. Excellent film surface smoothness after formation a resist pattern is also important. If a chemically amplified resist exhibiting poor film surface smoothness is used, irregularities (such as nano edge roughness) on the film surface is transferred to a substrate when a resist pattern is transferred to the substrate by an etching process or the like, giving rise to a decrease in dimensional accuracy and impaired electric performance in the ultimate devices (see, for example, J. Photopolym. Sci. Tech. P 571, 1998; Proc. SPIE Vol. 3333, p 313; Proc. SPIE Vol. 3333, p 634; and J. Vac. Sci. Technol. B16(1), 1998, p 69).
Development of a chemically amplified resist exhibiting excellent resolution and only slight nano edge roughness has therefore been desired.
In more recently, a chemically amplified resist containing a resin having an acetal group or a ketal group and one or more compounds selected from the group consisting of a diazomethane compound, triphenylsulfonium organic sulfonate compound, and diphenyliodonium organic sulfonate compound as a photoacid generator was proposed in Japanese Patent Application Laid-open No. 2000-284482. The inventors claimed that the resist possesses excellent characteristics such as high sensitivity and resolution capability, and to exhibit only minimal roughness on the pattern sidewalls.
However, development of a photoacid generator used for a chemically amplified resist containing a resin having an acetal group or a ketal group, particularly a resist exhibiting excellent resolution performance and small nano-edge roughness, has only just started. Successful development of a photoacid generator capable of deriving excellent performance from this type of chemically amplified resist is strongly desired from the viewpoint of development of technologies applicable to semiconductor devices which are increasingly being downsized.
An object of the present invention is to provide a radiation-sensitive resin composition useful as a chemically-amplified resist, sensitive to various radiations, particularly to far ultraviolet rays typified by a KrF excimer laser (wavelength: 248 nm), an ArF excimer laser (wavelength: 193 nm), or an F2 excimer laser (wavelength: 157 nm), as well as charged particles such as electron beams, exhibiting excellent resolution performance and pattern shape-forming capability, and suffering from a nano-edge roughness phenomenon only to a minimal extent.